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WIU Physics Professor Shows Lasing Without Inversion; Applications for X-Ray, Gamma-Ray Lasers

May 16, 2008

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MACOMB , IL - - Kishor Kapale, an assistant professor of physics at Western Illinois University, had his research, "Lasing Without Inversion: Counterintuitive Population Dynamics in the Transient Regime," published in the prestigious Physical Review Letters (PRL) vol. 100, article 173601 (April 29, 2008).

This was his second published paper in PRL during the 2007-2008 academic year.

Kapale's current research addresses the problem in understanding the generation of laser light through the phenomenon of lasing without inversion. Lasing without inversion is possibly the only way to obtain highly efficient X-ray and gamma-ray lasers, which are important for their practical uses in areas such as industrial, scientific, military and medical instruments, he said.

In 1917, Albert Einstein suggested a new phenomena regarding the interaction between light and matter named stimulated emission - - when light made up of a certain frequency or color falls on an atom, an interaction may occur to cause the atom to lose energy and emit light; causing the creation of lasers, Kapale explained. However, in order to sustain the laser output, the number of higher energy atoms in the sample needs to be larger than the lower energy atoms, which is a condition called population inversion.

"So the issue is that the population inversion condition makes it impossible to generate laser light in the X-ray or gamma-ray range of the electromagnetic spectrum because it requires enormous energy to begin with to excite atoms to such high energies, and we do not have good sources of X-ray and gamma rays," Kapale said.

His work with S. Ya Kilin of the Stepanov Institute of Physics, National Academy of Sciences of Belarus, and Marlan Scully of the Institute for Quantum Studies and the department of physics at Texas A&M University, shows how to understand lasing without inversion in a new light. The research demonstrates a novel method to manipulate the atoms in the sample so that even a small number of naturally existing high-energy atoms can cause laser light generation via lasing without population inversion. In the process, an initially more populated ground (lowest energy) state becomes more populated with time.

"This will allow the generation of X-ray and gamma-ray laser light without needing large energy input to begin with. This work will also allow for precise control of the behavior of a quantum system leading to its application in an important upcoming area of information processing known as quantum information," Kapale said.

Kapale's research interests include quantum optics, atom optics and quantum statistical mechanics; quantum information science; molecular physics and quantum chemistry; symbolic and numerical computation; and material simulations for non-linear optical properties. He has presented his research at some 41 conferences and universities across the U.S. and India; and he has written 25 articles which are in professional journals, two book reviews and six preprint articles.

Kapale, who was born in Maharashtra in western India, earned his bachelor's degree in physics (1995) from the University of Bombay; his master's degree in physics (1997) from the Indian Institute of Technology, Bombay; and his Ph.D. in theoretical quantum optics (2002) from Texas A&M University. He has been a postdoctoral research associate at Texas A&M University and Princeton University; he served two years as a National Research Council Research Associate (2004-2006) in the Jet Propulsion Laboratory (JPL) at the California Institute of Technology (Caltech); and was a senior postdoctoral researcher (2006-2007) at JPL-Caltech before joining Western Illinois University's physics faculty.

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